This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-261106, filed Sep. 14, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a probing method and probing system, and more specifically, a probing method and probing system ensuring an increase of the throughput.
A probing device 10 has a loading (loader) chamber 11, a probing (prober) chamber 12, a controller 13, and a display unit 14, as shown in FIG. 6. In the loading chamber 11, wafers W stored in a cassette C are taken out one by one and transferred to the probing chamber 12. The probing chamber 12 is adjacent to the loading chamber 11. The wafer W transferred from the loading chamber 11 is inspected in the probing chamber 12. The controller 13 controls the probing chamber 12 and the loading chamber 11. The display unit 14 is also used as an operation panel for controlling the controller 13.
In the loading chamber 11, tweezers 15 are provided via a rotary shaft. The tweezers 15 are used for transferring the wafer W. More specifically, the tweezers 15 take out the wafers W stored in the cassette C one by one and transfer them to the probing chamber 12 through back-and-forth movement in a horizontal direction simultaneously with clockwise-and-counterclockwise rotation. A sub-chuck 16 is provided near the tweezers 15, for prealigning the wafer W. The sub-chuck 16 receives the wafer W from the tweezers 15 and rotates clockwise and counterclockwise in a xcex8 direction, to prealign the wafer W by using an orientation flat of the wafer W as a reference.
The probing chamber 12 has a main chuck 17 for mounting the wafer W thereon. The main chuck 17 is moved in X and Y directions by means of X and Y stages 18, 19 and further moved in xcex8 and Z directions by built-in driving mechanisms. Furthermore, the probing chamber 12 has an alignment means 20 for aligning the wafer W with a probe card. The alignment means 20 has an alignment bridge 21 which has a first photographic means 21 (CCD camera or the like) for taking a picture of the wafer W, and a pair of guide rails 23, 23 which guide reciprocal movement of the alignment bridge 22 in the Y direction. A second photographic means (not shown), which is attached to the main chuck 17, is also included in the alignment means 20. The probe card (not shown) is provided above the upper surface of the probing chamber 12. The upper surface of the probe card is electrically connected to a test head (not shown) by way of a connection ring. The probe card receives a test signal from a tester by way of the test head and the connection ring, thereby inspecting electrical characteristics of an IC (formed on the wafer W) in contact with the probe.
More specifically, the IC on the wafer W is inspected as follows: first, a single wafer W is taken out from the cassette C by means of the tweezers 15 within the loading chamber 11. While the wafer W is transported by the tweezers 15 to the probing chamber 12, the wafer W is pre-aligned at a sub-chuck 16. In the probing chamber 12, the wafer W is passed from the tweezers 15 to the main chuck 17. Then, the alignment bridge 22 is moved above a probe center to align the wafer W on the main chuck 17 by means of the first photographic means 21 and the second photographic means attached to the main chuck 17. Thereafter, the wafer W is indexed by moving the main chuck 17 in the X and Y directions. After the main chuck 17 is moved up in the Z direction to allow the wafer W to be in contact with the probe, the main chuck 17 is overdriven. In this manner, each of the IC chips on the wafer w can be electrically in contact with the probe, with the result that electrical characteristics of each of the chips can be checked.
In the case of the wafer W having a size (diameter) of 200 mm or less, when the main chuck 17 is overdriven as shown in FIG. 7A, the wafer W mounted on the main chuck 17 is moved up along the z direction from the position indicated by a dash-dotted line to the position indicated by a solid line while being maintained almost horizontal, as shown in a solid line in FIG. 7A. During this period, the probe 24A of the probe card 24 is elastically lifted up from the position indicated by a dash-dotted line to the position indicated by a solid line in the FIG. 7A. The tip of the probe moves from a start point S to an end point E (indicated by a thick solid line). When the movement of the probe tip from the start point S to the end point E is viewed from above, the probe stays within the surface area of the electrode pad P of the IC chip, as shown by an arrow of the hatched line (see FIG. 7B). Since the probe 24A can maintain electrical contact with the electrode pad P, the electrical characteristics of the IC chip can be checked precisely.
However, if the size of the wafer is as large as e.g., 300 mm, the IC chip is not necessarily enlarged but miniaturized. Since the pitch between electrode pads is decreased, the number of pins of the probe card is accordingly increased up to about 2000. As a result, the load of the probe 24A applied on the main chuck 17 during the overdriving time results in, for example, 10 to 20 Kg. When the wafer W is overdriven from the position indicated by a dash-dotted line and comes into contact with the probe 24A, the load of the probe 24A is locally applied to the main chuck.
Due to the local application of the load, the rotary shaft (not shown) of the main chuck 17 is distorted, with the result that the wafer W is inclined by about 20-30 xcexcm, as shown by a solid line in the figure. That is, the wafer W is inclined outward from the position where the wafer W should be moved up. At that time, the tip portion of the probe 24A is lifted up from the position indicated by a dash-dotted line to the position indicated by a solid line in FIG. 8A. The moving distance is longer than the case shown in FIG. 7A. That is, the wafer moves as is indicated by a thick solid line in FIG. 8A. Although the start point S of the tip portion in this case is the same as that shown in FIG. 7A, the end point E is deviated from the electrode pad P as shown by a hatched arrow in FIG. 8B. Therefore, the tip portion may fall outside the electrode pad P. If this happens, a test signal cannot be sent from the probe 24A to the electrode pad P. As a result, the inspection will not be performed with high reliability.
The present applicant suggests a probing method and probing device in Japanese Patent Application No. 9-202476 for performing electrical inspection with high reliability by ensuring that a probe is in contact with an electrode pad of a wafer even if a load is locally applied to the main chuck. In this probing method, the correction amounts of the main chuck at the time of overdriving in the X, Y and Z directions are first obtained on the basis of data of the wafer chuck, wafer and probe card. The moving distances of the main chuck in the X, Y, and Z directions are corrected on the basis of the obtained correction amounts. In this way, the main chuck is overdriven.
FIG. 9 shows a system in which servo motors 31, 32 are employed as an X-axis driving mechanism and a Y-axis driving mechanism for moving a main chuck 17 in the X and Y directions, and a stepping motor 33 is used as a Z-axis driving mechanism for driving the main chuck 17 in the Z-axis. In this system, the stepping motor 33 differs in operational characteristics from the servo motors 31, 32. Therefore, it is virtually impossible to start or stop the driving of the servo motors 31, 32 simultaneously with the stepping motor 33. Conventionally, the motors 31, 32, 33 are independently driven and stopped.
The applicant found that if the X-axis motor, the Y-axis motor, and the Z-axis motor are driven alternately and separately in a plurality of steps on the basis of the signals from drivers and the stepping driver which are driven by the instruction from a host computer, in the aforementioned probing method, a probe moves in a zigzag movement to reach a target position (end point E), as shown in FIGS. 10 and 11. In this method, it is possible to ensure the probe to be in contact with an electrode pad. However, each of the motors is driven and stopped a plurality of times and the main chuck is moved in a zigzag manner, so that the throughput decreases.
The present invention is made to overcome the aforementioned problem.
An object of the present invention is to provide a probing method and probing system ensuring an increase of its throughput without driving a plurality of driving mechanisms in separate steps for moving the main chuck.
Another object of the present invention is to provide a probing method and probing system ensuring an increase of its throughput without driving a plurality of driving mechanism in separate steps even if a driving mechanism different in operational characteristics is employed as the driving mechanism for the main chuck.
Still another object of the present invention is to collectively and simultaneously control the X-axis driving mechanism, Y-axis driving mechanisms and Z-axis driving mechanism.
A further object of the present invention is that the X-axis driving mechanism, Y-axis driving mechanism, and Z-axis driving mechanism are collectively and simultaneously controlled by an imaginary controller operated on the basis of instruction signals sent from a host computer.
A still further object of the present invention is that the X-axis driving mechanism, Y-axis driving mechanism, and Z-axis driving mechanism are collectively and simultaneously controlled on the basis of control signals from the same protocol.
According to a first aspect of the present invention, there is provided a probing method for inspecting electrical characteristics of an object by probes, comprising the steps:
mounting the object on a main chuck having an X-axis, a Y-axis and a Z-axis which are driven by an X-axis driving mechanism, a Y-axis driving mechanism and a Z-axis driving mechanism, respectively;
moving the main chuck in X-, Y-, Z-directions by driving the X-axis, Y-axis and Z-axis by the X-axis driving mechanism, the Y-axis driving mechanism, and the Z-axis driving mechanism such that electrode pads of the object mounted on the main chuck are brought into contact with probes of probe card arranged above the main chuck; and
overdriving the main chuck toward the probe card by simultaneously and collectively controlling the driving mechanisms such that a tip portion of each the probes stays within a surface area of each of the electrode pads of the object.
In the probing method, the driving mechanisms are preferably controlled by an imaginary controller operated on the basis of instruction signals from a host computer.
In the probing method, it is preferable that the driving mechanisms be collectively controlled by control signals based on the same protocol.
In accordance with a second aspect of the present invention, there is provided a probing method for inspecting electrical characteristics of an object by probes, comprising the steps:
mounting the object on a main chuck having an X-axis, a Y-axis and a Z-axis which are driven by an X-axis driving mechanism, a Y-axis driving mechanism and a Z-axis driving mechanism, the Z-axis driving mechanism being different from the X-axis and Y-axis driving mechanisms in operational characteristics;
moving the main chuck in X-, Y-, and Z-directions by driving the X-axis, the Y-axis and the Z-axis by the X-axis driving mechanism, the Y-axis driving mechanism, and the Z-axis driving mechanism such that electrode pads of the object mounted on the main chuck are brought into contact with probes of a probe card arranged above the main chuck; and
overdriving the main chuck toward the probe card by simultaneously and collectively controlling the driving mechanisms on the basis of the same protocol by an imaginary controller which is controlled by instruction signals from a host computer such that each of probes stays within a surface area of each of the electrode pads of the object.
Preferably, the imaginary controller is constituted by software in the probing method.
In the probing method, the instruction signals from the host computer include at least one of data consisting of a target position of the main chuck to be overdriven and moving speeds of the main chuck in the X-, Y-, and Z-directions, driven by the X-, Y- and Z-driving mechanisms, respectively.
In accordance with a third aspect of the present invention, there is provided a probing system comprising:
a main chuck for mounting an object thereon;
X-, Y-, and Z-axis driving mechanisms for moving the main chuck in the X-, Y- and Z-directions, respectively;
a probe card arranged above the main chuck and having a plurality of probes electrically in contact with the object; and
a control mechanism for simultaneously and collectively controlling each of the mechanisms to overdrive the main chuck toward the probe card such that a tip of each of the probes stays within a surface area of each of the electrode pads of the object.
In the probing system, it is preferable that the control mechanism should have an imaginary controller which is connected to a host computer by way of a network line.
In the probing system, it is preferable that the driving mechanisms be collectively controlled by control signals based on the same protocol.
In accordance with a fourth aspect of the present invention, there is provided a probing system comprising:
a main chuck for mounting an object;
driving mechanisms for moving the main chuck in X-, Y- and Z-directions;
a probe card arranged above the main chuck and having a plurality of probes electrically in contact with the object;
a control mechanism for controlling the driving mechanisms so as to overdrive the main chuck after the main chuck is moved in the X-, Y-, and Z-directions by means of the driving mechanisms to bring the object into contact with the probes of the probe card, the control mechanism comprising;
a host computer;
an imaginary controller being operated on the basis of instruction signals from the host computer, the imaginary controller being controlled by software set therein and controlling the main chuck simultaneously and collectively in accordance with the same protocol such that each of the probes stays within a surface area of each of electrode pads of the object when the main chuck is overdriven.
In the probing system, it is preferable that the instruction signals from the host computer include at least one of data consisting of a target position of the main chuck to be overdriven and moving speeds of the main chuck in the X-, Y-, and Z-directions, driven by the X-, Y- and Z-driving mechanisms.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.